fix(corpus): make AuditReport.timestamp UTC-aware

[syf2211]

Summary

Make the default AuditReport.timestamp timezone-aware UTC instead of a naive local datetime.now().

Motivation

StalenessDetector and other corpus audit code use UTC-aware datetimes (datetime.now(UTC)). AuditReport.timestamp defaulted to naive datetime.now(), which is inconsistent and can raise TypeError when compared with aware datetimes.

Fixes #59

Changes

• openagent_eval/corpus/models.py: default timestamp factory now uses datetime.now(UTC)
• tests/unit/test_corpus/test_models.py: regression test asserting default timestamp is UTC-aware

Tests

• pytest tests/unit/test_corpus/test_models.py -q — 13 passed

Notes

• composer-2.5 review: APPROVE
• Commit author: syf2211 syf2211@users.noreply.github.com

[himanshu231204]

/oc review pr

[opencode-agent]

Review: APPROVE ✅

The change is correct and minimal:

• openagent_eval/corpus/models.py:71 — datetime.now() → datetime.now(UTC). The UTC import was already present (line 5). The factory now produces timezone-aware datetimes consistent with StalenessDetector and the rest of the corpus audit code, preventing TypeError when comparing aware vs naive datetimes.

• tests/unit/test_corpus/test_models.py:76-81 — Regression test asserts tzinfo is not None and tzinfo == UTC, covering the fix.

The test from the new test_default_timestamp_is_timezone_aware_utc passes (Python 3.12 confirms datetime.now(UTC).tzinfo == UTC). No lint or type issues. The PR references #59 correctly and follows the project conventions.

opencode session  |  github run

[github-actions]

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